In recent times, sleep has become a research topic of great interest. Sleep is a universal animal behavior that has significant import in modern human development and productivity. As a result, there is great motivation to study sleep, its benefits and the benefits that may be derived from optimizing sleep on an individual basis.
Electroencephalography (EEG) has been used pervasively in sleep research as a data collection tool due to its advantages in the field. Firstly, EEG creates reliable and reproducible quantitative results in a field that was, previously, largely qualitative. Secondly, it does so non-invasively by measuring electric signals at the scalp. Finally, during sleep, EEG signals have properties and behaviors that are largely invariant among varied populations. From EEG data, researchers have been able to accurately typify sleep stage cycles from EEG signals alone.
Sleep is known to be an episodic process with various stages, starting from a light state of sleep to a deeper state and back to the light state. When awoken during a light state of sleep, post-waking fatigue and sleep inertia (e.g. the desire to return to a sleeping state while waking) are reduced in physiologically healthy patients. Sleep stages can be typified by brainwave patterns and brainwaves during light sleep are similar to brainwaves while awake. The theta waves (4-7 Hz) that occupy most of Stage 1 and 2 sleep are significantly more analogous to the alpha waves (8-12 Hz) that dominate our awake state than the delta waves (0.5-2 Hz) of deep sleep. Most neural state changes (ex. being asleep to being awake) require some period of time for neurochemical and metabolic elements to direct the change; going from a state of light sleep to an awake state is faster than going from a state of deep sleep to an awake state. Because the transition from light sleep to an awake state is rapid, the duration of sleep inertia and fatigue should be minimized, as light state brainwave patterns are the most analogous to those observed in the awake state.